Provided is a storage system for solving the problem in that, when the registration of a nonexistent user is deleted, only a system administrator can access files that the user left, so that a load placed on the administrator increases at the time of an audit. The authentication program for permitting a user, who is attempting to log in to a storage system, to access a file recorded in the storage system, the program including: a first step for receiving a user name and a password from the user; a second step for referring to a validity term corresponding to a pair of the user name and the password recorded in the storage system; and a third step for permitting access by the user to a file corresponding to the validity term based on a result of the second step, the first to third steps being executed by a processor.